The VIP Membership DLC is an add-on that increases the game roster by 5 exclusive cars, and provides exclusive in-game benefits. VIP membership is included with the purchase of the Deluxe or Ultimate Editions of the game. This DLC is listed as "Bundle Only" during pre-order but VIP typically becomes a separately purchasable DLC after release that can be used to upgrade your Standard Edition (disc or digital).
VIP Cars
2015 Ferrari F12tdf
2015 Ford Falcon GT F 351
2016 Koenigsegg Regera
2016 Lamborghini Aventador LP750-4 SV
2015 Ultima Evolution Coupe 1020
VIP Benefits
VIP wheel spins with extra rewards each time you level up
access to exclusive online events
community gifts
"and more" (typically an icon for multiplayer/leaderboard display)
Shared DLC note
In previous Forza games, VIP cars have been accessible to other accounts on the same console as the owner account. However, VIP benefits have been limited to the DLC owner only, so other accounts have not had the VIP icon or extra wheel spin bonus. Other accounts on a shared console may need to purchase VIP DLC themselves if they wish to access these benefits (or FH3 may have changed its approach, TBA). For pre-order, this may mean needing to purchase a full edition bundle. When the dashboard Store indicates "installed" other accounts may be able to purchase from the Xbox Store (.com or app).